Updating Parent ZonesInternet Systems Consortium950 Charter StreetRedwood CityCA94063USmarka@isc.org
DNS UPDATE was developed to allow DNS zones to be updated.
There is a perception that UPDATE can not be used in conjuction
with the Registry, Registar, Registrant (RRR) model to update a zone.
This document explains how UPDATE can be used in the RRR model.
UPDATE is designed to update any zone in the DNS. This includes
updating delegating NS records, glue address records and DS record.
While UPDATE is primarily designed to UPDATE a zone directly
there in no reason why UPDATE requests cannot be translated to
the EPP requests to perform the changes.
This would provide a uniform model to update parent zone
regardless of where they are in the DNS heirachy.
The Registrar would host a server that authenticates UPDATE
requests received directly or relayed by the Registry using
TSIG , then translate the actions in
the UPDATE request into EPP transaction requests. The results
of those EPP transactions would be relayed to the UPDATE client.
Requests that are not TSIG signed are rejected.
The translating server would handle a restricted subset of
UPDATE requests, possibly ignoring the prerequiste section.
UPDATE requests would be limited to those supported by EPP.
e.g. Add NS record. Delete all NS records. Add A record.
Delete AAAA record. Add DS record. Delete DS record.
The translating server may also override/ignore the TTL in the
UPDATE request.
Authentication would be done using TSIG. TSIG was designed to
be used in a environment where requests are relayed.
Authentication can be done down to the <NAME,TYPE> tuple. There
exist nameservers that already implement access contols down to
this level of granuality based on the presented TSIG.
This would allow nameservers to update their own address records
as they get renumbered without being able to update anything else.
This would allow DNSSEC key management software to update DS records
without being able to update anything else.
As Registrars do all the authentication and generate the signed
responses there is no need for the Registry to have access to the
private material using in TSIG. Registrars already handle
shared keys in these numbers with their web interfaces.
The hardest part of Direct to Registrar is finding where to send
the UPDATE request. This would most probably just be advised to
the Registrant.
In the indirect model the Registry would host a UPDATE relay server
which would examine the first record of the UPDATE section and relay
the request to the Registrar of record for the owner name of that
record. The response would be relayed back.
The relay can use either TCP or UDP when forwarding UPDATE requests
as TSIG supports changes to the DNS id field when a request/response
is relayed.
This is consistent with how tools like nsupdate work out where to
send a UPDATE request. They look at the ownername of the first
record and use it to discover the containing zone.
UPDATE server discovery is a issue when the RRR model is in use as
the UPDATE may need to be directed through EPP and/or a sent to a
Registrar. There are a number of way this could be done.
Adding a underscore infix labels to the zone which contain SRV
records at pointing to Registar/Registry servers for each child.
e.g. <child>._update._tcp.<parent> SRV 0 0 0 server.example.tld
The servers pointed could be be a relay server, as described above,
or a UDPATE to EPP translating server. A relay server would allow
for slower zone growth.
Using underscore infix labels requires no changes to
nameservers operated by Registries but does require the
zone content to be updated.
Extend UDPATE to return the update server. Currently the
Zone section of the UPDATE refers to the zone to be update
and is identified by the <QNAME,SOA,QCLASS> tuple.
Replacing SOA with one or more of DS, NS, A and AAAA would
allow a nameserver to distingish between a traditional
UPDATE request and a request to find the UPDATE servers.
The tuple would contain the resource to be updated and the
reply would contain SRV records pointing to the UPDATE
servers. As there would possibly more than one parent the
owner records would refer to the parent zone being updated.
One could use a new OPCODE for UPDATE server discovery.
The UPDATE requests are all TSIG signed. This is a proven method
for securing UPDATE requests in the DNS.
Dynamic Updates in the Domain Name System (DNS UPDATE)Secret Key Transaction Authentication for DNS (TSIG)